high gain lee jackson gp 1000

[Smokebreak]

Sounds good ! Good work!

[Rune]

Very good Gorhrut, only thing different the tech did was a couple of diodes in series parralell to R204. But having a pot there kind of does the same thing. Sound almost spot on, need a litte more thightness, but thats RSP 2400s job and I still think the GP-1000 is in Samsamps loop for more gain and chrunch.
Didn't you do some 88'mods as well?

I might do the stability mod with my clone, but I think the pot is the main issue here. I think it is hooked up differently due to the second EQ, I have to check where the second EQs signal goes. I leaves mainboard after R205 it seems goes to the second EQ/masters PCB. Might also be a faulty part, or not grounded properly. Don't own any 1M replacements pots, only got some LIN 500k pots that came with some of my lower end guitars. The pot was always a known issue with the clone, the early prototype only had it working right (but still noise) with it set at minimum....

[Gorhrut]

Didn't you do some 88'mods as well?

just the tone stack update. from 47n and 100n to 100n and 200n. are there others?

[Gorhrut]

im working on mapping out a new layout and working in a power amp section then im going to make a full amp head out of this circuit.

i want to make sure i have it dead quiet when make this version.

[Rune]

Make sure to add an effects loop if you plan to put RSP2000 and/or Samsamp in the circuit. Great job on the amp. I will straighten out the trimpot issues later on, TWCC has told me he could still make me a new problem free main PCB. Or at least give me the layout so I could order one myself.

No, well except the MID pot to 50K (20K would also do). But Bodom uses it at the lowest setting (1) so I guess it actually means it's on full anyways.
You could also add more bass by changing the coupling capacitor C9 to 4400p and if you would like even more you could add a small capacitor to R205. Other than that I think the amp have plenty of treble already, and the mid-shift is still set on the value you need for "that" tone. And increasing values of C203-204 will add tightness.

This amp would have been more issue free and easier to mod with point to point layout.

[Gorhrut]

was looking inside my power amp and noticed it has 6550 tubes instead of kt88's. are these a direct swap?

also, this amp(vht 2/90/2) has 2 12ax7's and 2 12au7's. what are their functions and what effect does changing them have? between brands of tubes or tube types?

[Gorhrut]

@rune, do you have a schematic for the rsp 2400? or could you upload some pics?

[Rune]

No I havent and the only internal picture I know of is in the clone thread at Bodom forums. Yeah I got the unit, but Ive never opened it. You could ask TWCC for a clone or maybe buy a schematic from him. I couldn't be bothered to do all that, besides it would take a lot of time mapping it out. It's a very old early 1980s unit. Most of its components are ancient. But it seems like it is mostly made in PCB design with transistors and a lot of resistors, couldn't see many capacitors in threre, but it got a lot of LEDs for on/off buttons.

[Rune]

Haven't got around to more pot testing/replacing.
One Question thought; could I ground the pot to input instead of the pcb groundspot. I have reson to believe that it could be the issue. You see on my 88, my sold 87 transistional and the clone the groundspot is soooo close to the trace that goes to C4. While on gorhruts it is in the middle of the groundtrace.
As I see it, either the pot is defect, wired wrong or grounded wrong on all the editions Ive had/have in my property.
And the only difference I can see from gorhruts version is a more clean groundspot and a volume type pot instead of trimpot.

[Gorhrut]

sure, ground it where you like just not on the same point as the power supply. if youre mounting the pot on the back like mine, you might try ground points near the tube bases. to my understanding you want to keep grounding as short as possible. or you could drill a hole in that ground trace, but........

try it however you feel like and see if it works

[Cameron]

Haven't got around to more pot testing/replacing.
One Question thought; could I ground the pot to input instead of the pcb groundspot. I have reson to believe that it could be the issue. You see on my 88, my sold 87 transistional and the clone the groundspot is soooo close to the trace that goes to C4. While on gorhruts it is in the middle of the groundtrace.
As I see it, either the pot is defect, wired wrong or grounded wrong on all the editions Ive had/have in my property.
And the only difference I can see from gorhruts version is a more clean groundspot and a volume type pot instead of trimpot.

The grounding is not the problem...run the shielded cable like Lee did....

[Cameron]

Make sure to add an effects loop if you plan to put RSP2000 and/or Samsamp in the circuit. Great job on the amp. I will straighten out the trimpot issues later on, TWCC has told me he could still make me a new problem free main PCB. Or at least give me the layout so I could order one myself.

No, well except the MID pot to 50K (20K would also do). But Bodom uses it at the lowest setting (1) so I guess it actually means it's on full anyways.
You could also add more bass by changing the coupling capacitor C9 to 4400p and if you would like even more you could add a small capacitor to R205. Other than that I think the amp have plenty of treble already, and the mid-shift is still set on the value you need for "that" tone. And increasing values of C203-204 will add tightness.

This amp would have been more issue free and easier to mod with point to point layout.

Why do you think the sansamp is in a loop? The output of the preamp is the send of a loop and the return is the poweramp... no need for a loop here....and adding the loop will change the tone of this preamp.

Why do you think 1 is "full on"?

Increasing c204 205 will make it ...darker ...less highs ...not tightness IMO..
R205 (47k) should have a .001 cap already there..... again increasing this will cut the high end ....not add bass.

The best way to add bass.. without changing the tone too much is ...change the 50k trim to 1meg

[Gorhrut]

i think he mentioned effects loop because i said i am going to pair this preamp circuit with a poweramp circuit and turn them into a head.

[Cameron]

i think he mentioned effects loop because i said i am going to pair this preamp circuit with a poweramp circuit and turn them into a head.

But why the preamp in the loop of an amp? I could see it bypassing the pre of the amp but.. not both used. I don't see where Alexi did this at any time...can you point me to where he or its said that he did this. His tone is very simple to get...but when I see some of the info on forums ..its way over thought....and wrong.

[Gorhrut]

oh, youre talking about the sansamp.....that makes more sense.

i think rune suggested that as a way to further adjust the tone. idk how well it would work because i dont own one to try it out.